The present invention concerns a device for monitoring the condition of a spring employed subject to tension in a door or gate, especially a torque spring employed to equilibrate the one or more panels in an overhead door or roll-up gate and prevent the door or gate from slamming shut, dropping too rapidly. etc., the device including a blocker, a torque transmitter, a catcher, and a sensor and release assembly that senses the presence or absence of tension, whereby the torque transmitter specifically comprises a cable or chain-wound shaft or similar torque-accommodating component that is subject to the force exerted by the spring as long as the spring is intact, whereby, as the gate or door opens and closes, the blocker rotates around a shaft along with the torque transmitter and is mechanically coupled to an especially detented grabber, whereby the blocker can, subject to the grabber, block the rotation of the torque transmitter and hence the motion of the door, whereby the catcher can be shifted out of an inactive position, wherein it is disengaged from the grabber, and into an active position, wherein it engages the grabber, and whereby the sensor and release assembly constantly senses the presence or absence of tension in the spring and, if the spring breaks and the tension is accordingly eliminated, senses the absence and shifts the catcher out of its inactive position and into its active position, allowing the blocker to block the rotation of the torque transmitter.
A spring-condition monitoring device of the aforesaid genus is known from European Application 0 151 427 and its related patent, the entire disclosures in both of which are herein explicitly referred to.
One practical embodiment of this known spring-condition monitoring device is mainly intended to prevent an overhead door from falling when a torque spring that engages a shaft with a tensioning component, a Bowden cord, for example, wound around it breaks. Considerable torque must be accommodated when such a door is especially heavy, as is true of multiple-paneled factory doors for example. Some spring-condition monitoring devices must accordingly be designed to withstand torques of more than 800 Nm and reliably prevent shafts subject to considerable torque due to the weight of the door from spinning.
Previous attempts to solve this problem have relied on wheels on the shaft with ratchets that can be engaged by catches in the form of barrier pawls to prevent the motion. In its inactive position, the pawl is secured against a bolt in opposition to the direction the ratchet wheel is tensioned in. The bolt is part of a sensor and release assembly that senses the presence or absence of tension in the torque spring. If the spring breaks, the sensor and release assembly releases the bolt and allows it to disengage from the pawl. The bolt is for this purpose preferably directly connected to the torque spring""s seat, usually in the form of a resilient cone, and the spring""s tension forces it to engage with the pawl. The cone in one embodiment employed in spring-breakage safety devices in industrial gates can for this purpose pivot through a narrow range of angles around an axis that parallels the axis of rotation, allowing the bolt to carry out a rotation different from the circumferential direction around the axis of rotation and accordingly be easier to move out of the range of the barrier pawl and accordingly release.
Many other embodiments of the sensor and release assembly, however, electrical, electropneumatic, and pneumatic for example, are also conceivable. The sensor and release assembles in such embodiments can be strain gages or pressure gages for example instead of mechanical components.
There is, however, a drawback to the known spring-condition monitoring devices in that the require considerable space and material, especially when powerful torques necessitate longer radii for the ratchet wheel or similar blocker and hence a more complicated catcher. When access from outside is excluded, a housing around the known blocking mechanisms (blockers and catchers) will be necessary.
The object of the present invention is accordingly an advanced spring-condition monitoring device of the aforesaid genus that will occupy less space and preferably require less material as well while allowing even powerful torques to be blocked in the event of a broken spring.
This object is attained in accordance with the present invention in a spring-condition monitoring device of the aforesaid genus in that the wall of the blocker is essentially directed radially inward toward the axis, the grabber being mounted on the wall, and in that the catcher is provided with a section that is or can be accommodated radially inside the wall and can move radially outward into engagement with the grabber during its motion into the active position.
In contrast to the known ratchet wheel, which is an extra component with notches or similar structures, the blocker in accordance with the present invention accommodates the grabber in its interior, the catcher engaging it in an outward motion if the spring breaks. For the same grabbing radius, accordingly, the catcher can be much smaller and require less material than at the state of the art. A lower-mass catcher also has the advantage of less inertia, allowing more rapid blocking. Again, since a blocking mechanism comprising a blocker and a catcher accommodated inside it will be relatively well protected from exterior access and actions, no separate housing will be necessary. Still another advantage is that the blocker can be an annular section, a hollow flowerpot-shaped component preferably accessible from outside, or a drum.
The blocker in one particularly preferred embodiment of the present invention is at least part of, and preferably entirely, a drum that traction means can be wound around, the other end of the means being connected to the gate or door, preferably to the area at the bottom when the gate or door is closed. This blocker is accordingly not a separate component and can be integrated into a winding mechanism that is already present. In this embodiment, the entire spring-condition monitoring device itself can even be accommodated inside the winding mechanism, entirely enclosed, that is. The drum or winding mechanism itself can be or can be employed as a blocker more or less in the form of a hollow ratchet wheel. The result will be a large enough ratchet wheel with a long enough radius to comply with the space occupied by the drum or similar winding mechanism. The resulting lever arm will be long in relation to the axis of torque. Another major advantage of this embodiment is its extremely short force-application channel. When engaged, the force will flow from the gate or door through the traction means and hence directly to the catcher, which will divert the force out through its bearing. The force in the spring-condition monitoring device in accordance with the present invention will accordingly not flow into the torque shaft. An embodiment without a torque shaft is accordingly also conceivable when the torque is otherwise transmitted from the spring to the drum.
It will be preferable, because independent of sources of such outside energy as compressed air or electricity, for the catcher to be a mechanism of some sort, the catching section being provided on a barrier pawl that is radially outwardly resilient in relation to the axis of rotation and in particular spring-loaded, allowing it to engage detents on the radially inward-directed wall and accordingly constituting the grabber.
To ensure rapid and reliable release of the blocker in the event that the spring breaks, it is also preferable for the catcher to be provided with a supporting surface that during the inactive phase serves to support the catcher against a securing component that can be moved out of the way of the catcher by the sensor and release assembly in the event of a broken spring and that slopes in relation to the path of the securing component, allowing that component to be forced, as the catcher moves in the event of a broken spring, out of the path of the catcher and into the active position.
If for example a barrier pawl is employed as a catcher, the barrier pawl is mounted pivoting outside a traction-means shaft, the traction-means shaft serves as a torque transmitter, the barrier pawl is as at the state of the art retained in its inactive position by a securing component in the form of a bolt, the bolt is secured by a spring-loaded cone, and the spring-loaded cone is also mounted pivoting outside the shaft, only a transverse component of the barrier pawl""s tensioning force will be applied to the bolt, and will indeed be applied such as to ensure that the barrier pawl will rest against the bolt through the intermediary of the supporting surface, which does not extend perpendicular to the barrier pawl""s pivot. If the spring breaks and the spring-loaded cone moves along with the bolt through the accordingly provided range of angles around its pivot and into it final barrier position, the motion will be supported by the barrier pawl""s tension.
The catcher in another preferred embodiment of the present invention is a lever that pivots around an axis paralleling the axis of rotation and is resiliently tensioned into the active position with an arm that includes the catching section and especially the barrier pawl. When the lever includes another arm that operates in conjunction with the sensor and release assembly""s release mechanism and especially includes the supporting surface, the available space will be better exploited, and the actions used for releasing the blocker can be reversed. The second lever arm can in this event be employed for polling, of a spring-loaded cone motion in the event of a broken spring for example, a small component of the resilient pawl-tensioning force acting on the cone bolt by way of a steeply sloping plane (the supporting surface).
In the event of a broken spring, the release assembly, the bolt fastened to the spring-loaded cone or another securing device or the rest of the securing component will be tensioned not only into its or their release state but also backward impacting or backward bouncing. To prevent such a backward bouncing from reaching the once released second lever arm again, the second lever arm will pivot entirely out of range of the release mechanism and especially out of the path traveled by the securing component as the lever moves into the active position.
In one preferred version, the lever will be positioned to allow the first lever arm to be subjected in the active position to compressive force exerted by the blocking motion of the gate or door or similar structure. A lever arm thus subjected to compressive force offers advantages with respect to conserving material beyond those of a tensioned pawl in that it will lack the hook needed for a ratchet lever, and the free end of the arm can constitute a pawl-engagement section.
The first lever arm in another preferred embodiment of the present invention is a barrier pawl with a lug that engages one of the detents on the pawl and is provided with a sloping surface that slides over a matching sloping surface on the detent when the lever pivots in the event of a broken spring, allowing the lever to enter its final active position before any significant torque can be transmitted. The free end, constituting the catching section, of the first lever arm can itself act as or be provided with such a lug in the form of a bent section.
The embodiment with the matching sloping surfaces is of particular advantage in that traction-means drums are often extruded in a material that is more brittle than sheet metal for example. It will accordingly be of advantage for the forces that actually need to be accommodated to be initially applied when at all possible at the large-surface engagement between the lug and the matching detent flank. The grabber in the last advantageous embodiment hereintofore described drags over its sloping detent flank the equivalently sloping lug radially outward as far as the foot of the detent, allowing a large contact surface between the lug and the detent""s flank due to the associated sliding traction. This feature is of particular advantage in conjunction with a lever arm that can be subjected to pressure in that in an arm that is subjected to traction the slope of the flank would need to be so steep that in extreme cases the fracture resistance of the detents would suffer.
The radially inward-directed wall that supports (or constitutes) the grabber need not be continuous. It can be provided with gaps or even extend over only part of the circumference of the blocker. The wall need not be directed precisely radially inward in the geometrical sense. It can for example be provided everywhere with pawled areas to the extent that it will have no area perpendicular to the radial. What is important is that it face inward essentially or on the whole to the extent that the grabber provided on it will be radial accessible from inside.
Instead of being constantly radially inside the inward-directed wall, the catching section can assume a disengaged position during normal operation that is axially displaced for example outside the areas surrounded by the wall, while being in that area at least during the release motion, moving, that is, into the area during the release motion and radially outward in relation to the axis of rotation into the grasping position.